1. Field of the Invention:
The invention relates to component parts comprised of hard and elastomeric segments, in which the segments are rigidly bound together. The parts are manufactured by thermoplastic forming operations, using polyphenylene ethers (PPEs) and styrene-containing block copolymers.
2. Discussion of the Background:
Often a single material cannot contribute all the properties desired for an object. Such incompatible combinations of properties are, for example, high strength and stiffness combined with rubberlike elasticity and traction.
In order to invest component parts with properties not attainable in a single material, the parts are constructed as combinations of pieces comprised of different materials. In order for such parts to function satisfactorily, the pieces must be bonded together strongly and durably.
For objects comprised of thermoplastics and rubber, the bonding is ordinarily achieved by mechanical fastening, adhesive bonding, or covulcanization with the use of agents which serve as special covulcanization aids.
The strength of the bonding achieved by mechanical means is sufficient only for low stress applications.
In relatively large scale serial production, adhesive bonding is costly. In many cases, when an adhesive agent is used additional material related problems are introduced.
The most effective technique heretofore has been covulcanization of the stiff molded material and the rubber composition. This necessitates pretreatment of the surface of the stiff molded material and/or special treatment of the rubber composition.
One technique for surface-treating the thermoplastic consists of spreading an aqueous solution of vinylpyridine latex, resorcinol, and formaldehyde on the thermoplastic (See Nitzsche, L. H., Kautschuk and Gummi, Kunststoffe 36:572-6 (1983) and the 1972 monograph "Keilriemen" issued by Arntz-Optibelt-Gruppe Hoexter, published by Verlag Ernst Heyer, Essen, FRG, page 83). According to another method, the thermoplastic surface is treated with a gasoline solution of isocyanates ("Bayer-Taschenbuch fur die Gummi-Industrie", page 254 (1963)). Also, the rubber composition may have adhesion-promoting additives incorporated in it, for example, combinations of resorcinol, formaldehyde sources, silicic acid, zinc oxide, and fatty acids (Kleeman, W., "Mischungen fur die Elastverarbeitung", Leipzig, p. 300 (1982)).
There are a number of known binder systems comprising PPE-containing plastics and crosslinked rubbers. However, bonding is not achievable by thermoplastic processing in any of these systems.
Thus, in German OS No. 31 35 851, laminated bodies are described which are comprised of a natural or synthetic rubber and a partially crosslinked plastic.
It is known that SBR and EPR rubbers and polybutadienes display unexpectedly high adhesion to certain plastics after relatively long thermal treatment. These plastics, characterized by recurring p-oxyphenylene units, include poly(2,6-dimethyl-1,4-phenylene ether), polysulfones, and polycarbonates (Dreyfuss, P. and Runge, M. L., J. Appl. Polym. Sci. 23 (1979), 1863-66).
The processing conditions for these compounds correspond to those of vulcanization, i.e., curatives such as, e.g., peroxides and sulfur are necessary, and processing times are much greater than for thermoplastic processing methods.
German patent application No. P 36 02 705.7 of Jan. 30, 1986, which claims internal priority to German patent application No. P 35 07 506.6 of Mar. 4, 1985, describes a "method of producing a chemical bonding between PPE-based molding compositions and double-bond-containing sulfur-vulcanizable rubbers". Additionally, the rubbers used here are not subject to further thermoplastic processing.
German OS No. 27 18 481 (abandoned) asserts general claims for a three-layered bonded film strip comprised of two outer thermoplastic plastic layers and an inner, rubber-containing elastomer layer. However, what is disclosed is merely a film comprised of polyethylene as an outer layer and butyl rubber as an inner layer. The film can be manufactured by applying the rubbers in porous form onto a thermoplastic film, and then evaporating the solvent or coextruding the two materials. One skilled in the art is not able to infer from this publication any concrete teaching relating to bonding of other thermoplastic materials to elastomers.
A laminated material comprised of at least one PPE-containing layer A and at least one layer B containing at least 40 wt. % styrene is described in German OS No. 21 16 558. The styrene-containing layer may be comprised entirely of homopolystyrene; copolymers with up to 60 wt. % "hard comonomers" such as acrylonitrile, (meth)acrylic acid esters, or maleic anhydride; or 3-30 wt. % high impact polystyrene. A special embodiment in which pure isotactic polystyrene is used as the styrene polymer, or else a mixture of isotactic and atactic polystyrene is so used, is the subject of German OS No. 28 09 980 (abandoned). The laminated materials in both cases are quite intentionally limited to a combination of two hard plastic components. Therefore the proportion of styrene in layer B is always greater than 40 wt. %.